The Lincoln Park Zoo started small: two pairs of swans in 1868. Over the next 150 years, the zoo's animal population has expanded to more than 800 individual animals spanning 196 separate species -- not counting fish and insects.

Those numbers have fallen from the highest levels in the 1940s, '50s and '60s, as the zoo focused more on long-term species sustainability, says Jillian Braun, director of public relations for the zoo. In 2018, there are 60 percent fewer species at the zoo than there were 50 years ago.

Scaling back as focus changes

Number of species by animal type

In 2018:

Birds: 79

Mammals: 68

Reptiles: 35

Amphibians: 8

Invertebrates: 3

Fish: 3

Note: In 1892, there were birds at the zoo, but the number of species was unknown.

In the late 1800s, zoos operated under a "postage stamp collection" approach, Braun says, cramming as many different species as they could. Animal habitats were often small. In 1889, a Chicago Tribune article detailed neighbors' dissatifaction with the new sea lion exhibit: "... during the long watches of the night most of them, having no place to rest, swim back and forth in the pond and bark incessantly to express their disapproval of their cramped quarters."

That tactic has changed, and the number of animals has decreased as their habitats get larger and more complex. In 2016, the zoo opened a renovated, larger polar bear exhibit, an 8,400-square-foot space with a variety of different landscapes, taking the place of several other animal enclosures that held hyenas and other types of bears.

Counting every animal

Individual animals, by species

In 2018:

Birds: 317

Mammals: 311

Reptiles: 131

Amphibians: 60

Mouse over a bubble to see the animal and inventory.

The zoo is home to more than 800 individual mammals, birds, reptiles and amphibians, running the gamut from aardvarks to zebras. The largest groups of these species include 55 Chilean flamingos, 46 naked mole-rats and 25 Eastern Massasauga rattlesnakes. Don't look for all these animals at the same time, however. The zoo keeps some populations behind the scenes, Braun says.

These creatures come from around the globe, but early populations at the zoo focused on a North American-native population. A 1869 Hartfort Courant news article detailed the zoo's population, which included three wolves, one black bear, two bison and one racoon, among others.

Some of the largest animals at the zoo include three Eastern black rhinoceroses, two giraffes and four Bactrian camels. The smallest residents are hard to count, though.

Invertebrate populations such as about 5,000 Madagascar hissing cockroaches and 400 cichlids fish are estimated and inexact, Braun says. Honeybees are also counted by the colony (two) instead of by each individual bee.